1. Field of the Invention
The present invention generally relates to a semiconductor manufacturing system and, more particularly, to a vaporizer for vaporizing a liquid material to produce a gas to be used in a semiconductor manufacturing process.
2. Description of the Related Art
Generally, a semiconductor device is produced by processing a semiconductor wafer by repeating a film deposition process and a pattern etching process. Especially, requirements to the film deposition process have become more severe in association with the progress in a high density and high integration of semiconductor devices. For example, there is a demand for a thinner film with respect to an extremely thin film such as an insulating film for producing a capacitor or a gate in the semiconductor device. Also there is a demand for a thinner film with respect to an electrode film or a wiring pattern film. In a case of the wiring pattern film, there is suggested a method for depositing a copper or aluminum film by a chemical vapor deposition (CVD) method. In such a case, a film is deposited by using a deposition gas that is produced by vaporizing a liquid material. The liquid material is vaporized by a vaporizer so as to produce the deposition gas, which is a vapor of the liquid material. In a normal film deposition process, an amount of flow of the liquid material per unit time is extremely small. Accordingly, in order to perform a film deposition process with high accuracy, it is required to efficiently vaporize the liquid material supplied to a vaporizer and supply the vaporized material to the downstream side on which a film deposition apparatus is located.
A description will now be given, with reference to FIG. 1, of a structure of a conventional vaporizer. The conventional vaporizer 2 shown in FIG. 1 comprises a vaporizer body 4 in which a valve chamber is formed. The valve chamber 6 is divided into two chambers by a diaphragm 8, one is a valve chamber 6 and the other is a vaporizing chamber 10. The diaphragm 8 serves as a valve body, which opens and closes a valve port 12 so as to control a flow of the vaporized material.
The valve port 12 is provided in the center portion of the bottom of the vaporizing chamber 10 so that the liquid material supplied to the vaporizer 2 is discharged from the valve port 12. Additionally, a carrier gas inlet port 14 and a material gas outlet port 16 are provided on the bottom of the vaporizing chamber 10. The carrier gas inlet port 14 is provided for introducing an inert gas as a carrier gas such as Ar gas or He gas into the vaporizing chamber 10. The material gas outlet port 16 is provided for discharging the material gas, which is produced by vaporizing the liquid material in the vaporizing chamber 10. The discharged material gas is supplied to a film deposition apparatus (not shown in the figurer).
A linear actuator 18 is provided to the valve body 4 on the opposite side of the vaporizing chamber 10 with respect to the diaphragm 8. The linear actuator 18 includes a drive shaft 20 that protrudes into the valve chamber 6. The drive shaft 20 presses the diaphragm 8 so as to open and close the valve port 12 in a manner in which a degree of opening of the valve port 12 can be controlled. The entire vaporizer 2 is heated to a predetermined temperature by a heater (not shown in the figure) so as to promote vaporization of the liquid material by heating and prevent the material gas (vaporized liquid material) from being liquefied.
In the vaporizer 2, the vaporizing chamber 10 is evacuated to be in a predetermined negative pressure.
Accordingly, the liquid material supplied to the vaporizer 2 flows into the vaporizing chamber 10 through the valve port 12, and the liquid material is atomized and vaporized due to its adiabatic expansion within the vaporizing chamber 10 under the negative pressure environment. The thus-generated material gas is carried by the flow of the carrier gas, and discharged from the vaporizer 2 through the material gas outlet port 16 and supplied to the film deposition apparatus.
In the above-mentioned vaporizer 2, the diaphragm 8 having a small flexibility is used as an isolation wall between the valve chamber 6 and the vaporizing chamber 10. Thus, the volume of the vaporizing chamber must be very small, and, thus, the conductance of the vaporizing chamber 10 is small. As a result, the vaporizing chamber 10 cannot be set in a sufficient vacuum condition due to a pressure loss related to the configuration of the vaporizing chamber 10 even if a strong vacuum force is generated by the film deposition apparatus. Additionally, there is a problem in that a smooth flow of the material gas cannot be achieved due to the small conductance of the vaporizing chamber 10.
Accordingly, in the vaporizing chamber 10, the vaporization of the liquid material cannot be sufficiently performed, and atomized liquid material (mist of the liquid material) may adhere to an inner wall of the vaporizing chamber 10. Most of the atomized liquid material adhering to the inner wall of the vaporizing chamber 10 is gradually vaporized since the entire vaporizer 2 is heated to a predetermined temperature. However, in many cases the liquid material is a chemically unstable material, and the liquid material may decompose due to the heat reaction before being vaporized. Thus, there is a problem of a metal component being deposited on the inner wall of the vaporizing chamber 10, which closes the openings provided in the inner wall of the vaporizing chamber 10.
Additionally, Japanese Laid-Open Patent Application No. 5-304110 discloses a vaporizer in which an open/close valve and a flow control valve are provided as separate components. However, the vaporizer disclosed in this patent document has a problem in that the entire vaporizer becomes large.